In accordance with the requirements of citation databases, proper citation of publications appearing in our Quarterly should include the full name of the journal in Polish and English without Polish diacritical marks, i.e. "Eksploatacja i Niezawodnosc – Maintenance and Reliability".

Task „Implementation of procedures ensuring the originality of scientific papers published in the quarterly „Eksploatacja i Niezawodność – Maintenance and Reliability” financed under contract 532/P-DUN/2018 from the funds of the Minister of Science and Higher Education for science dissemination activities.

Numerical modelling of the thermal fatigue of steel WCLV used for hot forging dies

The paper presents an analysis of a numerical simulation of the low-cycle thermal fatigue of steel WCLV (X40CrMoV511) used in hot forging. As part of experimental studies a special test rig based on the rotating disc method was built and tests were carried out. Their results showed that the method can be used to reproduce the thermal fatigue conditions prevailing in the industrial forging process. For the given experimental conditions the instant when fatigue cracks appear was determined. A numerical model was built and the obtained finite element analysis results were compared with the laboratory test results in order to determine the amplitude of plastic strains at which a crack appears. As part of further research in the future the Coffin-Manson low-cycle fatigue model will be verified for other conditions and a low-cycle fatigue curve for steel WCLV will be determined.

Analysis of the impact of forging and trimming tools wear on the dimension-shape precision of forgings obtained in the process of manufacturing components for the automotive industry

The study presents the results of an analysis of the manufacturing process of a yoke-type forging for automotive industry with the use of numerical modelling and 3D scanning techniques, taking into account the gradual wear of both forging tools and trimming to determine the mutual impact of their operation on the dimensional accuracy of the forgings. The performed analysis included the 4 variants which are that have the most common place in the industrial process that is, for a combination of new and partly worn out die inserts (used during hot forging) and new and partly used cutting tools used for cold trimming. The first stage involved modelling of a hot die forging process. Next, the obtained results were implemented into second modelling stage, which involved a simulation of a cold trimming process of a flash, with the use of the normalized Cockcroft-Latham fracture criterion, with the consideration of eliminating the removed elements, for which the cracking value has been exceeded. The obtained results was verified by means of a case study under industrial conditions for the least favourable operating conditions of both types of tools and their impact on the dimension-shape precision of the forgings. These results allowed for a more complete analysis of the trimming process for a variety of operating conditions and the confirmation of the correctness of carried out numerical modelling, and thus the possibility of its use in combination with scanning technique to computer-aided manufacturing processes. The proposed solution allows the selection of optimum conditions for implementation of the processes of forging and trimming because of their use to provide the required net shape forgings.